Process for fabricating a semiconductor device

ABSTRACT

A polishing slurry prepared by dispersing in a dispersion medium, abrasive grains comprised of a material having a solubility in the dispersion medium at 25° C., of 0.001 g/100 g or higher is used to effectively remove any abrasive grains standing adherent to the surfaces of objects to be polished or the interiors of polishing apparatus after polishing.

[0001] This application is based on Japanese Patent Application No.2000-164650 filed in Japan, the contents of which are incorporatedhereinto by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to a polishing slurry suited for thepolishing of electronic materials, magnetic materials and opticalmaterials, a polishing method using the polishing slurry, and a processfor fabricating semiconductor devices.

[0004] 2. Description of the Related Art

[0005] In recent years, in order to achieve higher integration ofsemiconductor integrated circuits, wiring techniques more and more trendtoward finer and more multilayered wiring. This has brought about atendency toward a larger difference in height of interlayer insulatingfilms. Because of this difference in height of interlayer insulatingfilms, any wiring formed thereon may have a low processing precision anda low reliability. Hence, polishing techniques for improving smoothnessof interlayer insulating films have become very important For example,Japanese Patent Application Laid-open No.9-22885discloses chemicalmechanical polishing of interlayer insulating films formed onsemiconductor wafers.

[0006] Polishing slurries conventionally used for semiconductorsubstrate may include, e.g., as disclosed in Japanese Patent ApplicationLaid-open No. 11-111657, an acidic (about pH 3) alumina slurry, aneutral silica slurry having silica particles dispersed therein asabrasive grains, and an alkaline silica slurry prepared by adding sodiumhydroxide or the like to this neutral slurry. Besides these, as abrasivegrains, this publication further discloses oxide particles such asalumina particles, titanium oxide particles and zirconium oxideparticles obtained by hydrolyzing metal alkoxides.

[0007] Abrasive grains comprised of metals (inclusive of semi-metals) ormetal oxides, used in these conventional polishing slurries, adhere tothe surfaces of objects to be polished and to the interiors of polishingapparatus, e.g., to pads, dressers and so forth, and remain thereonafter polishing to damage smoothness and film properties unless nomeasure is taken therefor. Accordingly, as a post treatment ofpolishing, as disclosed in, e.g., Japanese Patent Application Laid-openNo. 9-22885, washing with an alkaline solution or scrubbing washing hasbeen carried out. However, for the abrasive grains comprised of metals(inclusive of semi-metals) or metal oxides, used in these conventionalpolishing slurries, it has been difficult to be completely removed bywashing, and has been very difficult to be removed by washing especiallywhen the abrasive grains stand stuck in the semiconductor substrate.

SUMMARY OF THE INVENTION

[0008] Accordingly, an object of the present invention is to provide apolishing slurry whose abrasive grains having remained after polishingare removable with ease, a polishing method and a semiconductor devicefabrication process which make use of this polishing slurry.

[0009] To achieve the above object, the present invention provides apolishing slurry comprising a dispersion medium and abrasive grainsdispersed in the dispersion medium; the abrasive grains comprising amaterial having a solubility in the dispersion medium at normaltemperature (25° C.), of 0.001 g/100 g or higher. The present inventionalso provides a polishing slurry comprising a dispersion medium andabrasive grains dispersed in the dispersion medium; the abrasive grainscomprising organic matter. In either of inorganic matter and organicmatter, the abrasive grains may preferably have a solubility in thedispersion medium, of 0.001 g/100 g or higher, and more preferably 0.1g/100 g or higher. In the case when the abrasive grains are comprised oforganic matter, it may preferably have a melting point of 30° C. orabove so that it can be present in the state of a solid in usualpolishing steps.

[0010] The present invention still also provides a polishing method ofpolishing an object to be poslished by using any of these polishingslurries of the present invention, and a process for fabricating asemiconductor device by using such a method.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] These and other features, objects and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings wherein;

[0012]FIG. 1A and FIG. 1B illustrate basic concept of the presentinvention; and

[0013]FIG. 2A to FIG. 2D are a cross-sectional views showing some stepsin a process of producing a semiconductor substrate.

DETAILED DESCRIPTION OF THE DRAWINGS

[0014] On the abrasive grains contained in the polishing slurry of thepresent invention, there are no particular limitations as long as theyare those having a solubility in its dispersion medium, of 0.001 g/100 gor higher at normal temperature, and capable of being present in thedispersion medium in the state of a solid. They may be comprised ofinorganic matter or organic matter, but may preferably be those which donot affect any properties of objects to be polished. For example, whenthe objects to be polished are semiconductor substrate members, it ispreferable to use materials which do not contain sodium, calcium or thelike.

[0015] Inorganic compounds usable as the abrasive grains in the presentinvention may include;

[0016] Ag compounds such as AgBr, AgCl, AgClO₄, Ag₂CrO₄, AgF, AgNO₃,Ag₂O and Ag₂SO₄;

[0017] Al compounds such as AlCl₃, Al(NO₃)_(3,) A₂ (SO₄)_(3,)Al(ClO₄)_(3 .)9H₂O, AlCs(SO₄)_(2 .)12H₂O, AlF_(3 .)3H₂O,AlK(SO₄)_(2 .)12H₂O, AlNH₄(SO₄)_(2 .)12H₂O and AlNa(SO₄)_(2 .)12H₂O;

[0018] As compounds such as As₂O₃;

[0019] Ba compounds such as BaBr₂, BaCl₂, Ba(ClO₃)₂, BaI₂, Ba(NO₂)₂,Ba(NO₃)₂, Ba(OH)₂, BaS and BaSO₄;

[0020] Be compounds such as Be(ClO₄)_(2,) Be(NO₃)₂, and BeSO₄;

[0021] Br compounds such as CaBr₂;

[0022] Ca compounds such as CaCO₃, CaCl₂, Ca(ClO₄)₂, CaCrO₄, CaI₂,Ca(IO₃)₂, Ca(NO₃)₂, Ca(OH)₂ and CaSO₄;

[0023] Cd compounds such as CdBr₂, CdCl₂, Cd(ClO₃)₂, Cd(ClO₄)₂, CdI₂,Cd(NO₃)₂ and CdSO₄;

[0024] Ce compounds such as Ce₂(SO₄)_(3,) Ce(IO₃)₃,Ce₂Mg₃(NO₃)_(12 .)24H₂O, Ce(NH₄)₂(NO₃)_(5 .)4H₂O, Ce(NO₃)₄,Ce(NH₄)(NO₃)₆ and Ce₂(WO₄)₃;

[0025] Co compounds such as CoBr₂, CoCl₂, Co(ClO₃)₂, CoI₂, Co(NO₃)₂ andCoSO₄;

[0026] Cr compounds such as Cr(NO₃)₃ and CrO₃; Cs compounds such asCsCl, CsClO₃, CsClO_(4 ,) CsI, CsNO₃ and Cs₂SO₄;

[0027] Cu compounds such as CuBr₂, CuCl₂, Cu(ClO₃)₂, Cu(NO₃)₂, CuSO₄,CuCl_(2 ,) Cu(ClO₄)_(2 .)6H₂O, CuCrO₄, CuF_(2 .)2H₂O, CuI, CuI₂,CuK₂(SO₄) .6H₂O, Cu(NH₄)₂Cl_(4 .)2H₂O, Cu(NH₄)₂(SO₄)_(2 .)6H₂O,CuSeO_(4 .)5H₂O, Cu(SiF₆) .4H₂O and Cu(SO₃NH₂)₂;

[0028] Fe compounds such as FeBr₂, FeCl₂, FeCl₃, Fe(ClO₄)₂,Fe(ClO₄)_(3,) Fe(NO₃)₂, Fe(NO₃)_(3,) FeSO₄, FeF₃ 3H₂O,FeK₂(SO₄)_(2 .)6H₂O, FeNH₄(SO₄)_(2 .)12H₂O and Fe(NH₄)₂(SO₄)_(2 .)6H₂O;

[0029] Ge compounds such as GeO₂;

[0030] B compounds such as H₃BO₃;

[0031] Cl compounds such as HClO₄ H₂O;

[0032] P compounds such as H₃PO₄;

[0033] Hg compounds such as HgBr₂, HgCl₂, Hg₂Cl₂, and Hg(ClO₄)₂;

[0034] I compounds such as I₂;

[0035] In compounds such as InCl₃;

[0036] K compounds such as KBr, KBrO₃, K₂CO₃, KCl, KClO₃, KClO₄, K₂CrO₄,K₂Cr₂O_(7,) KF, K₃[Fe(CN)₆], K₄[Fe(CN)₆], KHCO₃, KH₂PO₄, K₂HPO₄, KI,KIO₃, KIO₄, KMnO₄, K₂MnO₄, KNO₃, KOH, K₃PO₄, KSCN, K₂SO₃, K₂SO₄, KHF₂,KHSO₄ and KNO₂;

[0037] La compounds such as LaCl₃, La(NO₃)₃ and La₂(SO₄)₃;

[0038] Li compounds such as LiBr, LiBrO₃, Li₂CO₃, LiCl, LiClO₄, Li₂CrO₄,LiI, LiNO₃, LiOH and Li₂SO₄;

[0039] Mg compounds such as MgBr₂, MgCO₃, MgCl₂, Mg(ClO₃)₂,Mg(ClO₄)_(2,) MgCrO₄, MgMoO₄, Mg(NO₃)_(2,) MgSO₃ and MgSO₄;

[0040] Mn compounds such as MnBr₂, MnCl₂, Mn(NO₃)₂ and MnSO₄;

[0041] Mo compounds such as MoO₃;

[0042] NH₄ compounds such as NH₄Br, NH₄Cl, NH₄ClO₄, (NH₄)₂CrO₄,(NH₄)Cr₂O_(7,) NH₄F, NH₄HCO₃, NH₄H₂PO₄, (NH₄)₂HPO_(4,) NH₄I, NH₄NO₃,NH₄SCN, (NH₄)₂SO_(4 ,)(NH₄)₂S₂O₈, (NH₃OH)Cl, (NH₄)₂CO₃, NH₄HF₂, NH₄N₃and NH₄NO₃;

[0043] Na compounds such as NaBO₂, NaBr, NaBrO₃, NaCN, Na₂CO₃, NaCl,NaClO₂, NaClO₃, NaClO₄, Na₂CrO₄, Na₂Cr₂O_(7,) NaF, Na₄[Fe(CN)₆], NaHCO₃,NaH₂PO₄, Na₂HPO₄, NaI, NaIO₃, NaMnO₄, NaNO₂, NaNO₃, NaOH, Na₄P₂O₇, Na₂S,NaSCN, Na₂SO₃, Na₂SO₄, Na₂S₂O₃, Na₃VO₄ and Na₂WO₄;

[0044] Nd compounds such as NdCl₃, Nd(NO₃)₃ and Nd₂(SO₄)₃;

[0045] Ni compounds such as NiBr₂, NiCl_(2,) Ni(ClO₃)_(2,) Ni(ClO₄)_(2,)Ni(NO₃)₂ and NiSO₄;

[0046] Pb compounds such as PbBr₂, PbCl_(2,) PbI₂, Pb(NO₃)₂ and PbSO4;

[0047] Pr compounds such as PrCl_(3,) Pr(NO₃)₃ and Pr₂(SO₄)₃;

[0048] Pt compounds such as PtCl₄, [PtCl(NH₃)₅]Cl₃ and [Pt(NH₃)₆]Cl₄;

[0049] Rb compounds such as RbBr, RbCl, RbClO₃, RbClO₄, Rb₂CrO₄,Rb₂Cr₂O_(7,) RbI, RbNO₃ and Rb₂SO₄;

[0050] Sb compounds such as SbCl₃;

[0051] Se compounds such as SeO₂;

[0052] Sm compounds such as SmCl₃;

[0053] Sr compounds such as SrBr₂, SrCl_(2,) Sr(ClO₃)_(2,) Sr(ClO₄)₂,SrI₂, Sr(NO₂)₂, Sr(NO₃)_(2,) Sr(OH)₂ and SrSO₄;

[0054] Th compounds such as Th(NO₃)₄ and Th(SO₄)₂;

[0055] Tl compounds such as TlBr, TlCl, TlClO₄, TlNO₂, TlNO₃, TlOH andTl₂SO₄;

[0056] U compounds such as U(SO₄)₂UO₂CrO₄, UO₂(NO₃)₂ and UO₂SO₄;

[0057] Y compounds such as YBr₃, YCl_(3 ,) Y(NO₃)₃ and Y₂(SO₄)₃;

[0058] Yb compounds such as Yb₂(SO₄)_(3;) and

[0059] Zn compounds such as ZnBr₂, ZnCl₂, Zn(ClO₂)_(2,) Zn(ClO₃)₂,Zn(ClO₄)_(2,) ZnI₂, Zn(NO₃)₂ and ZnSO₄.

[0060] Of these, it is preferable to use Al compounds, Ce compounds, Cucompounds, Fe compounds and/or NH₄ compounds. In particular, NH₄compounds are preferred because they do not deteriorate anysemiconductor products. As the most preferred materials for abrasivegrains, they may include NH₄Cl, NH₄ClO₄, NH₄HCO₃, Ce₂(SO₄), CuCl₂ andCuSO₄.

[0061] As specific examples of the organic matter usable as the abrasivegrains in the present invention, it may include organic acids (organicacids and esters or salts thereof), alcohol compounds, ether compounds,phenolic compounds and nitrogen-containing compounds. These organiccompounds are commonly formed of crystals softer than inorganic matterand hence may hardly scratch polishing objects Thus, these areparticularly advantageous for polishing soft objects such as insulatingfilms formed of organic materials or oxides of metals or semi-metals.

[0062] The organic acids may include adipic acid, acetylsalicylic acid,salts of benzoic acid (such as potassium benzoate and strychininebenzoate), o-nitrobenzoic acid, p-hydroxybenzoic acid, carbamic esters(such as ethyl carbamate), salts of formic acid (such as potassiumformate and magnesium formate dihydrate), citric acid, citric acidhydrate, chloroacetic acid (i.e., α-chloroacetic acid, β-chloroaceticacid or γ-chloroacetic acid), succinic acid, salts of oxalic acid (suchas ammonium oxalate and potassium oxalate), oxalic acid hydrate,tartaric acid (i.e., (+)-tartaric acid or (−)-tartaric acid), nicotinicacid, nicotinic acid hydrochloride, maleic acid, malonic acid,DL-mandelic acid, DL-malic acid, salts of valeric acid (such as silvervalerate), salts of gluconic acid (such as potassium gluconate), saltsof cinnamic acid (such as calcium cis-cinnamate), salts of acetic acid(such as uranyl acetate dihydrate, calcium acetate, cesium acetate,magnesium acetate tetrahydrate and lithium acetate dihydrate), salts ofsalicylic acid (such as ammonium salicylate, potassium salicylatehydrate), trichloroacetic acid, salts of naphthalene sulfonic acid (suchas ammonium 1-naphthalene sulfonate and ammonium 2-naphthalenesulfonate), hippuric acid, hippuric esters (such as ethyl hippurate),salts of phenoxyacetic acid (such as ammonium phenoxyacetate), salts offumaric acid (such as calcium fumarate trihydrate), salts of butyricacid (such as calcium butyrate hydrate and barium butyrate), and aminoacids.

[0063] As the amino acids, usable are, e.g., L-ascorbic acid, glycine,DL-α-aminoisobutyric acid, aminobutyric acid (such as DL-α-aminobutyricacid, 3-aminobutyric acid or 4-aminobutyric acid), aminopropionic acid(such as DL-alanine, L-alanine or β-alanine), orotic acid ester salts(such as ethylammonium orotate and benzylammonium orotate), andDL-valine.

[0064] The alcohol compounds may include saccharides such as D-glucose,D-glucose hydrate, sucrose and D-mannitol, and salt of glycerophosphoricacid (such as calcium glycerophosphate). The ether compounds may include18-crown-6. Incidentally, the saccharides listed here aremonosaccharides and disaccharides, and may also be trisaccharide orhigher polysaccharides.

[0065] The phenolic compounds may include catechol, 2-naphthol,m-nitrophenol, hydroquinone, resorcinol, glycidylglycine and pyrogallol.

[0066] The nitrogen-containing compounds may include amine compounds,amide compounds, imide compounds, nitro compounds, ammonium salts, andheterocyclic compounds containing nitrogen as a heteroatom. Statedspecifically, usable are acetanilide, acetamide, aniline hydrochloride,ethylenediaminetetraacetic acid, caffeine, urea, thiourea,2,4,6-trinitrotoluene, phenylenediamine (i.e., o-phenylenediamine,α-m-phenylenediamine, β-m-phenylenediamine or p-phenylenediamine),acrylamide, antipyrine, quinine salts (such as quinine hydrochloridedehydrate and quinine sulfate heptahydrate), cocaine hydrochloride,codeine phosphate dehydrate, succinimide hydrate, taurine, tetraethylammonium salts (such as tetraethylammonium chloride, tetraethylammoniumbromide and tetraethylammonium iodide), tetrapropylammonium salts (suchas tetrapropylammonium iodide), tetramethylammonium salts (such astetramethylammonium bromide and tetramethylammonium iodide),tris(hydroxymethyl)aminomethane, pyrazole, pteridine andhexamethylenetetramine.

[0067] Of these, adipic acid, citric acid hydrate and malonic acid arepreferred because the metal copper can be prevented from corroding.Sucrose is also preferred because it makes it easy to dispose of wasteliquor and does not deteriorate any semiconductor products.

[0068] There are no particular limitations on the dispersion medium aslong as it is a liquid capable of dissolving these abrasive-grainmaterials. For example, the following materials (1) to (5) are usable asthe dispersion medium.

[0069] (1) An acidic solution (preferably pH 2 to 4) containing at leastone acid selected from hydrofluoric acid, hydrochloric acid, sulfuricacid, nitric acid, acetic acid and organic acids.

[0070] (2) An alkaline solution (preferably pH 9 to 11) containing atleast one base selected from ammonium hydroxide, potassium hydroxide,sodium hydroxide and amines.

[0071] (3) A solution containing a salt of the above acid with the abovebase.

[0072] (4) Water.

[0073] (5) An organic solvent (preferably an aliphatic alcohol having 1to 5 carbon atoms.

[0074] The dispersion medium may optionally further contain hydrogenperoxide and ammonium fluoride, and may also appropriately containadditives such as an anti-corrosive and a dispersant. For the purpose ofstable dispersion of the abrasive grains, it is desirable for theabrasive-grain material to stand dissolved in saturation in thedispersion medium. The abrasive-grain material standing dissolved in thedispersion medium may also function as a surface-active agent, adispersant, an anti-corrosive, a buffer or the like.

[0075] In the present invention, the dispersion medium may optionallystill further contain at least one of a cationic surface-active agent,an anionic surface-active agent, an amphoteric surface-active agent andan organic solvent. Such various surface-active agents may each be usedin a concentration not higher than the critical micellar concentrationor not higher than 0.01 mol/L based on the total weight of thedispersant, in order to avoid agglomeration of abrasive grains andensure a stable dispersibility.

[0076] The abrasive grains in the present invention may have any graindiameter without any particular limitations, and may appropriately bedetermined in accordance with polishing objects, smoothness required,and so forth. To obtain abrasive grains having a specific size, a methodis available in which the above abrasive grains, having been dried, arepulverized and then classified with a sieve. Another method is alsoavailable in which a solution having the abrasive grains dissolvedtherein is atomized by means of an atomizer, and the abrasive grainsstanding atomized are collected and then dried, followed byclassification with a sieve.

[0077] The abrasive grains in the present invention may be dispersed inthe polishing slurry in a quantity (i.e., quantity of abrasive grainspresent in the form of a solid, per unit volume, or weight, of thepolishing slurry) which may appropriately be determined in accordancewith polishing objects, smoothness required, polishing rate and soforth, and may preferably be in an amount of from 1 to 50% by weight,and more preferably from 1 to 20% by weight, based on the total weightof the polishing slurry. In order to leave the abrasive grains in theform of a solid without being dissolved in the dispersion medium, thepolishing slurry may be prepared by adding the abrasive grains to thedispersion medium in a quantity exceeding the solubility of theabrasive-grain material. Accordingly, the quantity of the abrasivegrains used may appropriately be determined in accordance with polishingconditions (the quantity and type of the slurry, pH, temperature,additives and so forth).

[0078] The polishing slurry of the present invention makes use of theabrasive grains that can be dissolved in the dispersion medium. Hence,the quantity in which the abrasive grains are dispersed in the polishingslurry can dynamically be changed in the course of polishing, bychanging, e.g., the quantity and/or temperature of the dispersionmedium. Stated specifically, in the present invention, the quantity ofdispersion of the abrasive grains to be dispersed in the polishingslurry in the form of a solid can be changed by changing the quantity ofthe dispersion medium in the polishing slurry. More specifically, in thepresent invention, the dispersion medium may be added to the polishingslurry so as to make the abrasive grains dissolve in part in thedispersion medium to lower their quantity of dispersion. Conversely, thedispersion medium may be removed in part from the polishing slurry so asto recrystallize the abrasive-grain material having stood dissolved inthe dispersion medium, thus abrasive grains can be made to form anew tomake the abrasive grains become dispersed in a larger quantity. Also,the temperature of the polishing slurry may be changed so as to changethe solubility of abrasive grains in the dispersion medium to change thequantity of dispersion of the abrasive grains dispersed in the polishingslurry in the form of a solid.

[0079] The present invention also provides a polishing method ofpolishing an object to be polished, by using the polishing slurry of thepresent invention, and a process for fabricating a semiconductor deviceby using this polishing method. The polishing slurry of the presentinvention is suited for polishing electric or electronic materials,magnetic materials and optical materials, such as resins, conductors andceramics, and is especially suited for polishing conductor films andinsulating films, in particular, those of semiconductor devices, wiringsubstrates and so forth, in the manufacture of electric or electronicapparatus for which a high smoothness and a high cleanness are required.

[0080] For example, as shown in FIG. 1A, abrasive grains 1 standadherent to the surface of a semiconductor wafer member 2, afterinterlayer insulating films such as plasma silicon oxide films, CVD(chemical vapor deposition) silicon oxide films and PVD (physical vapordeposition) silicon oxide films have been smoothed by chemicalmechanical polishing. However, according to the present invention, theabrasive-grain material increases in solubility because of the heatgenerated by polishing, and hence the abrasive grains become dissolvedin the dispersion medium, so that the abrasive grains 1 may less adhereto the surface of the object to be polished. Also, the abrasive grains 1having adhered may be dissolved in a wash liquid, whereby, as shown inFIG. 1B, they can completely be removed with ease. Thus, compared withconventional polishing slurries, a clean polished surface can much moreeasily be obtained. Incidentally, as the wash liquid, any liquid capableof dissolving the abrasive-grain material, such as the solvent used inthe dispersion medium, may appropriately be selected.

[0081] According to the present invention, any abrasive grains standingadherent to the surfaces of objects to be polished such as semiconductorsubstrates or to the interiors of polishing apparatus after polishingcan be removed in a good efficiency, and hence semiconductor productsand so forth can be manufactured at a low cost, in a high quality and ata high yield. Moreover, according to the present invention, the quantityof dispersion of abrasive grains in the dispersion medium can becontrolled with ease, and hence the polishing wear or polishing rate candelicately be controlled. Also, since the abrasive grains can be made todissolve, the disposal of waste liquid can be made without separatingthe abrasive grains from the polishing slurry. Incidentally, the presentinvention is applicable not only to semiconductor wafers but also tosubstrates of thin-film devices, thin-film disks and the like.

THE PREFERRED EMBODIMENT

[0082] Examples of the present invention are given below, which aredescribed with reference to FIG. 2A to FIG. 2D. The present invention isby no means limited to these Examples.

[0083] In the present Examples, polishing slurries were prepared inwhich abrasive grains (grain diameter: 150 nm) comprised of compounds asshown in Table 1 were dispersed in an amount of 30 g per 100 g ofpolishing slurry, and, using these, oxide films were polished to smoothsemiconductor substrate surfaces. In Table 1, the solubility of eachcompound at normal temperature (25° C.) is shown together. TABLE 1Abrasive-grain Solubility material (%) Example 1  NH₄Cl 28.2 InorganicExample 2  NH₄ClO₄ 21.0 matter Example 3  NH₄HCO₃ 19.9 Example 4 Ce₂(SO₄)₃ 7.59 Example 5  CuCl₂ 42.8 Example 6  CuSO₄ 18.2 Example 7 adipic acid 2.4 Organic Example 8  citric acid 62.0 matter monohydrateExample 9  succinic acid 7.5 Example 10 ammonium oxalate 5.0 Example 11sucrose 67.0 Example 12 malonic acid 32.2

[0084] (1) Preparation of polishing slurry:

[0085] First, to a solution prepared by dissolving NH₄HCO₃ particlessaturatedly in an ammonia solution with a pH adjusted to 11, abrasivegrains having a primary particle diameter (particle diameter ofindividual abrasive grains) of 30 nm and a secondary particle diameter(particle diameter of abrasive grains standing agglomerated) of 150 nmwere further added in an amount of 30 g per 100 g of polishing slurry,and dispersed therein to obtain each polishing slurry.

[0086] (2) Polishing conditions:

[0087] As the polishing apparatus, a polishing apparatus manufactured byApplied Materials, Inc. was used, and polishing objects were polishedsetting the number of revolutions of the head at 90 rpm and the numberof revolutions of the platen at 90 rpm and feeding a 25° C. polishingslurry at a feed rate of 200 mL/minute. Here, polishing temperature wascontrolled to 25° C. so that the liquid temperature did not rise duringpolishing.

[0088] (3) Production of semiconductor substrate member:

[0089] First, as shown in FIG. 2, an oxide film 4 was formed on asemiconductor substrate 3, and an Al wiring 5 was further formed thereonto produce a semiconductor substrate member having a difference inheight at the surface [FIG. 2, (a)]. On the surface of this substratemember, a silicon nitride film 6 serving as a polishing stopper layerwas so formed as to cover the uncovered surfaces of the oxide film 4 andwiring 5 [FIG. 2, (b)].

[0090] Subsequently, an oxide film 7 was so formed by CVD as to fill upthe difference in height that was formed by the wiring 5 [FIG. 2, (c)].Thereafter, by means of the polishing apparatus, this oxide film 7 wasso polished as to provide a smooth surface, using the polishing slurryprepared in the above step (1). Thus, a semiconductor substrate member 9having an interlayer insulating film 8 having a smooth surface wasobtained.

[0091] Finally, this substrate member 9 was washed with water by meansof a brush washing assembly manufacture by Dainippon Screen Mfg. Co.,Ltd. to remove abrasive grains remaining thereon, and thereafter thesurface of the oxide film 7 was observed with an optical microscope anda scanning electron microscope. As the result, neither scratch norabrasive grain buried in the oxide film 7 was seen, and it wasconfirmable that the oxide film 7 was provided with a good smoothnesswhen any polishing slurries of Examples 1 to 12 were used.

[0092] Percentage of rejects of semiconductor substrate members obtainedin the respective Examples was smaller by 5% than a case in whichsubstrate members were polished using a conventional polishing slurry(silica particles of a primary particle diameter of 30 nm and asecondary particle diameter of 150 nm were used as abrasive grains,which were dispersed in an ammonia solution with a pH adjusted to 11).Thus, it has become apparent that the polishing slurries of the aboveExamples enable manufacture of semiconductor products in a high qualityand at a high yield.

[0093] While we have shown and described several embodiments inaccordance with our invention, it should be understood that disclosedembodiments are susceptible of changes and modifications withoutdeparting from the scope of the invention. Therefore, we do not intendto be bound by the details shown and described herein but intend tocover all such changes and modifications fall within the ambit of theappended claims.

What is claimed is:
 1. A process for fabricating a semiconductor device,comprising: forming a thin film on a semiconductor substrate; andpolishing a surface of said thin film, wherein the surface of said thinfilm is polished by using a polishing slurry comprising a dispersionmedium and abrasive grains dispersed in the dispersion medium, saidabrasive grains being comprised of a material having a solubility in thedispersion medium, at 25° C., of at least 0.001 g/100 g.
 2. The processaccording to claim 1, wherein said abrasive grains contain at least oneselected from the group consisting of Ag compounds, Al compounds, Ascompounds, Ba compounds, Be compounds, Br compounds, Ca compounds, Cdcompounds, Co compounds, Cr compounds, Cs compounds, Cu compounds, Fecompounds, Ge compounds, B compounds, Cl compounds, P compounds, Hgcompounds, In compounds, K compounds, Li compounds, Mg compounds, Mncompounds, Mo compounds, NH₄ compounds, Na compounds, Nd compounds, Nicompounds, Pb compounds, Pr compounds, Pt compounds, Rb compounds, Sbcompounds, Se compounds, Sm compounds, Sr compounds, Th compounds, Tlcompounds, U compounds, Y compounds, Yb compounds, Zn compounds and I₂.3. The process according to claim 1, wherein said abrasive grains arecomprised of organic material having a melting point of at least 30° C.,and further said organic material contains at least one selected fromthe group consisting of organic acids, organic acid esters, organic acidsalts, alcohol compounds, ether compounds, phenolic compounds andnitrogen-containing compounds.
 4. The process according to claim 3,wherein said dispersion medium is: (1) an acidic solution containing atleast one acid selected from the group consisting of hydrofluoric acid,hydrochloric acid, sulfuric acid, nitric acid, acetic acid and organicacids other than acetic acid; (2) an alkaline solution containing atleast one base selected from the group consisting of ammonium hydroxide,potassium hydroxide, sodium hydroxide and amines; (3) a solutioncontaining a salt of the above acid with the above base; (4) water; or(5) an organic solvent.
 5. The process according to claim 4, whereinsaid dispersion medium further contains at least one of cationicsurface-active agents, anionic surface-active agents, and amphotericsurface-active agents.
 6. A process for fabricating a semiconductordevice, comprising: forming a thin film on a semiconductor substrate;and polishing a surface of said thin film, wherein: said polishing iscarried out by supplying on the surface of said thin film a polishingslurry comprising abrasive grains dispersed in a dispersion medium; anda quantity of dispersion of said abrasive grains is varied in the courseof said polishing.
 7. The process according to claim 6, wherein, in saidpolishing, said abrasive grains in part are dissolved or precipitated inthe dispersion medium, so as to vary the quantity of dispersion of theabrasive grains dispersed in the dispersion medium in the form of asolid.
 8. The process according to claim 6, wherein, in said polishing,the solubility of the abrasive grains in the dispersion medium is variedby changing the temperature of the polishing slurry, so as to vary thequantity of dispersion of the abrasive grains dispersed in thedispersion medium in the form of a solid.